The invention relates to planetary-type wire-feeding mechanisms for converting a rotational motion of a motor shaft to a prescribed linear force along a first axis for selectively advancing an elongated wire.
In one known system of this type suitable, e.g., in electric arc-welding systems, an electrode wire is forwardly advanced along a first axis and through a welding tube by a pair of skewed rollers, such rollers being carried by a pair of pistons which are supported for reciprocation in a radial direction on opposite sides of the feed axis. The rear portion of the housing is connected to the shaft of a drive motor, so that upon a rotation of the motor the resultant turning movement of the housing about its axis will be effective to impart a planetary movement to the skewed rollers. When the pistons are urged inwardly into a wire-engaging position, the skewed surfaces cooperate with the wire to advance the wire in screw thread-like fashion through the welding tube.
In certain such designs, an adjusting nut is engageable with a threaded rear portion of the feed housing, such nut being manually adjustable to vary the force of the skewed rollers on the associated wire in proportion to the degree of turning of the nut.
A disadvantage of the last-mentioned arrangement is that the degree of adjustment by turning the nut is subjective and inexact. In addition, in such scheme, the respective movements of the pistons, and thereby of the skewed rollers, against the opposed surfaces of the advancing wire tend to be uneven and non-symmetrical, leading to binding and inefficiencies of wire feed.